The invention relates to bearings in general and foil thrust bearings in particular.
Foil thrust bearings are very attractive for high speed rotating machinery because they do not require oil-based lubrication and the maintenance demands of an oil-based lubrication system. Instead of using oil, foil thrust bearings use a process fluid such as air, methane, water, or gaseous or liquid hydrogen, nitrogen or oxygen.
Metal foils, spring assemblies and other components of the foil bearings can be difficult to manufacture. In the spring assembly, for example, a unitary spring cluster is spot-welded to a spring stiffener disc. Spot-welding places restrictions on the types of materials that can be used for the spring cluster and the stiffener disc. Dissimilar metals for the spring cluster and the stiffener disc cannot be used, even though such use might be desirable.
Fabricating spring clusters for the spring assemblies can be difficult, especially for large bearings. A spring cluster is fabricated by chemically etching spring sectors in a very thin sheet of metal. For small foil bearings this is feasible but complex. However, as the rotating machines become larger, and larger foil thrust bearings are needed, fabricating a large spring cluster from a single sheet of very thin metal will become even more complex and possibly unfeasible.
Welded spring clusters can also lead to maintenance problems. If a single spring sector in the spring cluster is damaged, the spring cluster cannot be unwelded from the stiffener disc. Instead, the entire spring assembly must be replaced.